Core for electrical apparatus



E. C. GEORGE CORE FOR ELECTRICAL APPARATUS Sept. 25, 1928.

Filed Dec. 27, 1926 Patented Sept. 25,1928.

NITED STATES 1,585,742, PATENT OFFICE.

EDGAR c. GEORGE, F NORWOOD, OHIO, AssIGnoa T0 ALLISLCHALMERS MANUFACTUR- ING COMPANY; 01? MILWAUKEE, WISCONSIN, A CORPORATION 01 DELAWARE.

001m FOB ELECTRICAL APPARATUS.

Application filed December 27, 1926 Serial No. 157,043.

This invention relates in general to electrical apparatus, and it has more particular relation to features of construction of the cores of such apparatus which effectively Contribute to reduce the losses occurring in rent losses in the core, and to assemble and hold these core laminae in assembled relation through the use of spaced clamping bolts. However, these clamping bolts along with the securing means therefor, such as nuts, riveting or the like, when in operative position, especially in dynamo-electricmachines where the element is made up of core laminae clamped between rigid end heads which serve as or constitute the essential support for the core member, cause the laminae to 'bearfiatwise against each. other with such pressure as to cause undue reduction of the resistance between adjacent laminae and thus undue increase in; the eddy current losses due thereto.

The present invention contemplates and includes a design and construction which embodies the advantages of reducing eddy currentlosses through utilizing thin core laminae, and also securing the laminae in assembled relation in a mechanically satisfactory manner, but with such increased re sistance of the path between adjacent laminae as-resultsin considerably reduced eddy current losses, while'pern'iitting economies in the matterot cost ofmanufacture. I

It is an object of the presentinvcntion to provide an improved design and construc tion of cores for electrical apparatus of the type assembled from relatively thin laminations, which provides ample security in the matter of mechanical assembly and'construd tion and increasedadvantages in the matter oi electrical cliiciency. p lta further object of the present inven tion to provide an improveddesign and construction-of apparatus of this character, wherein the pressure exerted 'on the core laminae for holding the samein' assembled condition is notfully applied throughout no1'malflux-carrying portions of the laminae.

It is a further object of the'present invention to provide an impmveq de gn and QQIb struction of apparatus of the above character, wherein the pressure exerted on the laminae in holding the same in assembled condition is applied to the full extent on portions of the laminae outside of: the normal flux-carrying portions thereof, permitting the latter portions to bear one against another with reduced pressure.

These and other objects and advantages are attained by the present invention, various novel features of which will be apparent from thedescription and drawings, disclosing an embodiment'oi the invention, and

will bemore particularly pointed out in the claims.

In the drawings:

Fig. 1 is an end view, with parts broken away, of a dynamo-electric machine embodyingfeatures of the presentinvention.

Fig. 2 is a tragmental sectional view in the plane of the line II-II of Fig. 1. a

Fig. 3 is a. view in elevation of a detail of the apparatus shown in Figs. 1 and 2.

In accordance with the drawings, a dynamo-electric machine, which may be considered an induction motor, of the open stator frame type, is shown as having the stator frame made upof two spaced end heads 10, 12, preferably of cast steel, and the core-13 of the stator is made up of a bundle of thin annular core la ninations, preferably with spaced projections 14 at the outer periphery, 'as indicated, these core laminae being held clamped in operative position between the end heads 10, 12 by bolts 15 or the like passing through ,alined apertures in the end heads and the peripheral projections 14, on the core laminae. These peripheral enlargements 14 on the core laminae are of such size as to form a substantial hearing or supportingarea for the clamping bolts 15 passing through apertures in the enlargements of such size to just receive these bolts, the apertures being preferably wholly outside of the edge of the normal flux-carrying path through, the core. The bolts 15 may be considered as including a head port-ion cooperative with the outer side of the end headlO, and a nut 16 In the ordinary construction of a machine of this general character, the rotor comprises a core 23. made up of laminae assembled and clamped between end plates, and a winding 2%, oi the squirrel cage type, having its induced port-ions disposed in slots of the core. The shaft of the rotor is supported in bearings formed on end bells or housings 26 carried by the end heads 10. 12; and the motor is supported by feet, preferably cast integral with the end heads 1-0, 12 of the stator.

The ordinary commercial practice in the matter of the construction of cores, for dynamo-electric machines of the laminated core type has heretofore been to provide a bundle of thin sheet steel laminae which are formed to the desired shape, the laminre being varished usually by dipping in an in sulating varnish bat-h. These laminae are assembled and clamped between end heads to provide the desired degree of mechanical compactness and support of the assembled core. However, even with the clamping bolts and apertures therefor in the peripheral enlargements formed on the core laminae radially beyond the active flux-carrying portion of such laminae, in clamping these laminae or punchings against each other so as to provide a desirable and secure mechanical arrangement, sufficient pressure must be exerted between the flux-carrying portions of adjacent laminae to reduce the resistance between such laminae, thus causing increased eddy current losses.

In order to avoid this objectionable feature of the described prior art construction and also to secure an equally satisfactory and even more desirable construction at no appreciable increase, and usually at a con siderable decrease, in cost of manufacture, these laminae, instead of being clam aed tightly one against another throughout substantially their full area, are so assembled as to be separated into small bunches or groups spaced apart by thin separators or spacers 31 disposed about and held in position on the clamping bolts 15 which pass through apertures in the peripheral enlargements H of the laminae. These spacers 31 are preferably oi. substantiallf, the same size and shape as the peripheral enlargements 14: of the lamime, with sufiicient material about the apertures in the spacers to permit the latter to maintain themselves on the bolt 15. These spacers 31 may be of metal, such as steel, but they are preferably of insulating material, such as paper or fiber. for the latter has the effect of reducing the resistance of any path of eddy currents through the lamina? at these points.

lVith the desired number of lamina-1 assembled with thin spacers 31disposed in position about or upon the clamping bolts 15 at short intervals throughout the length of the core to divide the latter into small groups of laminze, it is possible to exert the desired clamping pressure on the lamime and end heads between which the lamina: are secured, to insure the desired mechanical strength and security of the assembled core; and this desired clan'iping pressure and mechanical security is attained without the necessity of arising the active or normal fluxcarrying portions of the laminae to bear on or against each other with such pressure as reduces the resistance of the path between adjacent laminae to the point of unduly increasing eddy currents and core losses.

In commercial practice involving the use of core laminae oi a thickness probably between .010 inches and .025 inches, especially desirable results have been secured with the spacers 31 of paper about .013 inches in thickness disposed about .375 inches apart, that is, thus forming groups of lamina: approximately .375 inches thick.

A very substantial manufacturing economy is associated with the use of the present invention, by reason of the fact that unvarnished core plates .or laminae may now be used in accordance with the present invention with the same and even better results as to operating efficiency in the matter of core losses than with varnished core laminae assembled and held together in accordance with the prior commercial practice wherein the full clamping pressure used for securing the laminae in assembled condition was exerted over substantially the full area of the active fluxecarrying portions of the laminae.

It should be understood that the invention claimed is not limited to the details of construction and design described herein, for various modifications within the scope of the claims will occur to persons skilled in the art.

It is claimed and Letters Patent:

1. In a core for electrical apparatus, assembled core laminae provided with circumferentially spaced peripheral enlargements, enlargements on several laminae being axially alined,'spacing devices disposed between certain of said laminze at portions thereof adjacent said peripheral enlargements and extending inwardly therefrom to an inappreciable extent into the active flux-carrying path through said core, and means for clamping said laminae together in a mechanically secure condition, said clamping means being associated with the peripheral enlargements of said laminae and said spacing devices whereby the normal flux-carrying portions of said laminae are permitted to bear one against another with less pressure than the peripheral enlargements of said laminae.

2. In a core for electrical apparatus, as-

desired to secure by sembled core laminae provided with circumferentially spaced peripheral enlargements,

enlargementson several laminae being axially alined,qthin spacersbetween the peripheral enlargements of; certain adjacent ones of said laminae, and clamping means for said laminae associated with the peripheral enlargements of said laminae and saidspacers and effective to clamp said laminaein assemlaminae being axially alined, thin. apertured spacers between the peripheral enlargements of certain adjacent ones of said laminae, and clamping bolts passing through alined apertures in the peripheral enlargements of said. laminae and said spacers and effective to clamp said laminae in assembled condition with a less degree of compression between the normal flux-carrying portions ofsaid laminae than between the peripheral enlargements thereof. a l

4. In a core for electrical apparatus, assembled core laminae provided with circumferentially spaced and axially alined peripheral enlargements, thin spacers between certain adjacent ones of said laminae and cooperative with substantially only the peripheral enlargements of said laminae, and

clamping means associated with the peripheral'enlargements of said laminae and said spacers and operative to secure said laminae in assembled condition with a less degree of compression between the normal flux-carrying portions of said laminae than between the peripheral enlargements thereof.

5L In a core for electrical apparatus, a pair of spaced and apertured end plates, assembled core laminae provided with circumferentially spaced and apertured peripheral enlargements, enlargements on the several laminm being axially alined, thin apertured spacers between the peripheral enlargements of certain adjacent ones of said laminae, and clamping bolts passing through alined apertures in said end'plates, the peripheral enlargements of said laminae and said spacers and effective to clamp said laminae in assembled condition with a less degree of compression between the normal fiuxcarrying portions of said laminae than a between the peripheral enlargements thereof.

6. In a dynamo-electric machine, a pair of spaced end heads, core laminae provided with peripheral enlargements beyond the normal flux-carrying path of the laminae assembled between said end heads, spacers between the peripheral enlargements of certainof said laminae, and means assoolated with the peripheral enlargements of said laminae and cooperative with said end heads for clamping said laminae in assembled and operative condition between said end heads with a less degree of compression between the fluxcarrying portions of saidlaminae than between the peripheral enlargements thereof.

7. In a dynamo-electric machine, a pair of'spaced and "apertured end heads, core laminae provided with apertured' peripheral enlargements beyond the normal flux-carrying path of the laminae assembled between said end heads, apertured spacers between the peripheral enlargements of certain of said laminae, and clamping bolts passing through alined apertures in'said end heads, the peripheral enlargements of said laminae and said spacers, said clamping bolts having means associated therewith for caus- 1ng said bolts'to hold said laminae and spacers in assembled operative condition between said end heads.

8. In a dynamo-electric machine, a pair of spaced end heads, unvarnished core laminae provided with peripheral enlargements beyond the normal flux-carrying path of the lamina assembled between said end heads, spacers between the peripheral enlargements of certain of said laminae, and

means associated with the peripheral enlargements of said laminae, and cooperative with said end heads for clamping said laminae in assembled and operative condition between said end heads with a less de gree of compression between the flux-carrying portions of said laminae than between the peripheral enlargements thereof.

9. Ina dynamo-electric machine, a pair of spaced and apertured end heads, unvarnished core laminae certain of which are provided with apertured peripheral enlargements beyondthe normal fluxcarrying path of said laminae assembled between said end heads, thin spacers between certain of said laminae and cooperative with substantially only the peripheral enlargements of said laminae, and clamping means for said laminae comprising a bolt passing through alined apertures in said end heads and the peripheral enlargements of said laminae and operative to secure said laminae in assembled condition between said end heads with a less degree of compression between the normal fluXcarrying portions of said laminae than between the peripheral enlargements thereof.

10. In a core for electrical apparatus, assembled core laminae having their normal fluxcarrying' portions substantially uninsulated one from another, spacing devices interposedbetween groups of said'laminae and bearing upon only a portion of the abutting laminae removed from the mostactive part of said flux-carrying path, and clamping means for said laminae associated therewith and with said spacing devices and effective to mechanically secure the latter and said laminae in operative assembled condition while permitting portions of said laminae out of the Zone of full bearing, of said spacing devices to bear against one another with substantially less pressure than the portions of said laminae more directly associated with said spacing devices.

11. In a core for electrical apparatus, assembled core laininaa having their normal flux-carrying portions substantially uninsulated one from another, said laminae being provided with circumterentially spaced peripheral enlargements the enlargements of several laminae being axially alined, spacing devices interposed between groups of said laminae in line with the peripheral enlargements thereof and bearing against the abutting laminae over an area substantially less than that of the active flux-carrying portion thereof, and clamping means for said laminae associated therewith and with said spacing devices and effective to mechanically secure the latter and said lamina; in operative assembled condition while permitting portions of said laminae out of the zone of bearing of said spacing devices to bear against one another with substantially less pressure than the portions of said laminae more directly associated with said spacing devices.

In testimony whereof the signature of the inventor is aflixed hereto.

EDGAR G. GEORGE. 

